Conventionally, a CMP apparatus used in a process for manufacturing semiconductor integrated circuit devices has been configured to polish a surface of a semiconductor wafer to be polished by, for example, pressing a semiconductor wafer (object being polished) held on the lower surface of a top ring to which a rotative force is given by a rotational axis supported on an arm against a surface of a polishing pad mounted on a polishing table to which a rotative force is given by a rotational axis, while feeding a polishing liquid to the surface.
In this type of CMP apparatus, frictional heat generated due to friction between the polishing surface and the wafer rises, if a process of raising the pressure of the polishing surface of the polishing pad, a process of raising the relative velocity between the polishing surface and the semiconductor wafer, or the like is performed when the semiconductor wafer is being polished, in order to increase a polishing rate. Thus, the temperature of the polishing surface and the polishing liquid (slurry) spreading across the polishing surface rises. Along with this temperature rise in the polishing surface and the slurry, a temperature rise is also caused in the semiconductor wafer in contact with the polishing pad and the slurry and in the top ring holding the semiconductor wafer.
The temperature rise in the polishing surface of the polishing pad degrades the hardness and Young' modulus of the polishing pad and may cause a degradation in the degree of planarity of the surface of the semiconductor wafer being polished which is an object to be polished. If the temperature of the slurry rises, the polishing rate can be expected to increase for reasons of the chemical performance of the slurry. If the temperature rises excessively, however, the properties of the slurry degrade. The slurry thus may fail to deliver its intrinsic polishing performance. In addition, any significant rise in the temperature of the top ring holding the wafer affects a mechanism for pressing the wafer against the polishing pad. Accordingly, there is the desire to be able to manage and control these temperature rises due to polishing.
Hence, it is known that a cooling plate is placed in contact with the polishing surface of the polishing pad to remove heat therefrom by means of thermal conduction (see, for example, Japanese Patent Laid-Open No. H9-123057). In this cooling by a thermal contact conductance method, however, the cooling plate has contact with the polishing pad and the slurry. Accordingly, there arises the need for devices for coating and cleaning a surface of the cooling plate to be brought into contact with the polishing pad, in order to prevent contamination resulting from the cooling plate (contamination by ions and particles). In addition, if slurry particles generated as the result of the slurry adherent to the cooling plate being dried drop from the cooling plate onto the upper surface of the polishing pad, these slurry particles may be caught between the polishing surface of polishing pad and the polished surface of the wafer during wafer polishing and cause damage to the polishing and polished surfaces. Thus, there arises the need for a device for cleaning the cooling plate as a whole.
Yet additionally, since a heat removal effect in a thermal contact conductance method is proportional to the contact area of the cooling plate and the temperature difference between the cooling plate and the polishing pad (or the slurry), the contact area and the temperature difference have to be large. It is not easy to secure such a contact area, however, since a top ring holding the wafer, a dresser for dressing the pad, a slurry nozzle for feeding the slurry, an atomizer nozzle (high-pressure pure water shower nozzle) for cleaning a pad surface, and the like are disposed above the surface of the polishing pad.
Hence, it is known that the latent heat of vaporization is removed by spraying a dry gas (air or nitrogen) onto the surface of the polishing pad wetted with slurry and the like (see, for example, Japanese Patent Laid-Open Nos. 2012-139739 and 2013-22664). If a dry gas is sprayed onto the surface of the polishing pad, however, the slurry splashes due to the dry gas thus sprayed and the amount of slurry components effective for polishing decreases. Another problem is that the splashed slurry attaches to locations around a CMP apparatus and the slurry thus attached drops to cause a scratch problem in wafer surfaces. This method is therefore inferior in general versatility and is narrow in the range of application.
Hence, the present inventors have paid attention to a spatial exhaust flow rate in a space of polishing treatment, particularly in the vicinity of the polishing surface of the polishing pad. Thus, the present inventors have conceived of being able to manage and control the amount of latent vaporization heat released from the surface of the polishing pad, the slurry, and the surface of the top ring and, thereby, manage and control a temperature rise in the polishing pad and the like by managing and controlling the exhaust flow rate.
That is, an object of the present invention, which has been accomplished in view of the above-described problems, is to set the temperature of a predetermined location inside a processing space in which a polishing pad and the like are disposed to within a predetermined temperature range, for example, a temperature range in which a polishing rate is maximum.